Photographic emulsion.



UNITED STATES PATENT OFFICE.

PHOTOGRAPHIC EMULSION.

Specification of Letters Patent.

Patented Dec. 1, 1908.

' Application filed August 13, 1907. Serial No. 388,427.

To all whom 'it may concern:

Be it known that I, JACQUES THEODORE GATEAU, citizen of the FrenchRepublic, residing at Aix-en-Provence, France, have invented certain newand useful Improvements in Photographic Emulsions, of which thefollowing isa specification.

The present invention relates to a photographic emulsion for pigmentprinting. Up to the present for said printing process sensitive mixtureshave been used which consist of chrome-compounds and albuminoussubstances. It is further known to employ a mixture of common albumenwith ferric ammonium citrate.

According to the present invention instead of the chrome compounds,ferric salts, cerium-salts and uranium-salts are employed and they arenot mixed with the common albumens or with any other albuminoussubstance whatsoever, but with alkaline-albuminates or acidic albumens.These albuminates and albumens are substances which are insoluble inpure water, but which are soluble without any alteration by means ofneutral salts, alkalies or acids, and which can again be precipitatedfrom these solutions, (animal or vegetable caseins and similarmaterials). When these derivates of albumens are exposed to the lightafter they have been mixed with a ferric salt which, when exposed to thelight decomposes in developing an insoluble oxid, they become lesseasily soluble in their ordinary solvents. In this manner emulsions canbe produced by means of ferric salts, cerium salts and uranium salts,the sen'sitiveness of which isnearly equal to the sensitiveness ofchromesalt emulsions and which consequently are adapted to replace saidchrome-salt emulsions.

To produce the colloidal substances, the albuminous substances aredissolved in water, to which previously a solvent (ammonia, borax,carbonate of soda etc.) has been added; hereupon the ferric salt isadded and further the pigment and the emulsion is spread on a glass slabor paper. The sensitiveness of the sensitive paper which has thus beenproduced, can be further increased through the addition of coloringsubstances,

'- such as, for example, metallic violet etc.; in

this manner the papers are sensitized for the yellow and red rays.

After the paper has been exposed behind a plate, the photograph isdeveloped in a bath which is adapted to dissolve the albuminoussubstance (ammonia, carbonate of Ewamples.

1.-5 grams of anhydrous casein is dissolved in 7 5 grams of Water, whichcontains 2 cubic centimeters of ammonia. 2% grams of ferric ammoniumcitrate are added, pigment is admixed and the substance is spread onpaper.

2.The ferric ammonium citrate of the compound described in Example 1.may be replaced by 2 grams of sulfate of cerium and 5 decigrams oftartaric acid, which are dissolved in ammoniac water.

What I claim as my invention is A photographic emulsion for pigmentpaper consisting of one of the albumens which are insoluble in purewater but soluble without any alteration by means of neutral salts,alkalies and acids, and which can be precipitatedfrom their solutions,and of a ferric salt admixed with the said albumen.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

JACQUES THEODORE GATEAU.

" Witnesses ALLAN MAGFARLANE, GEORGE WASHINGTON.

